Microglanis garavelloi, new species, collected in tributaries of rio Paranapanema and rio Tietê, is the first species of the genus described from upper rio Paraná basin. The new species can be distinguished from other species of Microglanis on morphometric characters, color pattern, caudal-fin shape, pectoral-spine morphology and lateral line development. Characters used specifically to distinguish M. garavelloi from M. cottoides (laguna dos Patos and rio Uruguay basins) and M. parahybae (rio Paraíba do Sul basin) include morphometrics, color pattern and pectoral-spine serration.

Microglanis was proposed by Eigenmann (1912) as a monotypic genus to include the species Microglanis poecilus. The genus is easily distinguished from other Pseudopimelodidae by its small adult size (no greater than 11 cm SL), premaxillary tooth plate with rounded lateral margin and no posterior extension, and an incomplete lateral line (Eigenmann, 1912; Gomes, 1946; Mees, 1974).

The 13 species of Microglanis are distributed in the Orinoco and Amazon basins, one Pacific coast drainage in Ecuador, the Maracaibo basin (rio Catatumbo), lago Valencia and Caribbean drainages in Venezuela, Atlantic coastal drainages of the Guianas and eastern and southern Brazil from the rio São Francisco to the state of Rio Grande do Sul, and Uruguay basin (Mees, 1974; Shibatta, 2003; Bertaco & Cardoso, 2005; Mori, 2005). Prior to this study, Microglanis had not been reported from the rio Paraná basin despite extensive collections from this region.

A recent collection in the rio Tibagi, in Paraná State, Brazil, revealed a population of a new species of Microglanis. Additional specimens were subsequently discovered in museums collected from the rio Tietê basin, São Paulo State, Brazil, in Promissão, Cosmópolis, and Botucatu municipalities. The specimens from the basins of Tibagi and Tietê rivers were found to represent a new species described herein as Microglanis garavelloi. A morphometric analysis was performed to distinguish M. garavelloi from M. parahybae and M. cottoides, distributed in the Paraíba do Sul and Uruguay basins respectively, because M. parahybae has a similar pattern of coloration and the new species was misidentified as M. cottoides by previous authors (e.g. Visotto et al., 1999).

Material and Methods

Measurements were taken point-to-point with digital caliper to 0.01 mm, following Malabarba & Mahler (1998), except for body depth, which was taken at the dorsal-fin origin. The new species, M. parahybae and M. cottoides were compared using size-free canonical variate analysis (SFCVA) in order to test hypothesized differences among the species and to identify diagnostic characters. The program SAS was used to calculate the SFCVA, according to the method developed by Reis et al. (1990). Meristic data include numbers of pectoral-fin rays, pelvic-fin rays, dorsal-fin rays, caudal-fin rays, gill rakers, vertebrae, and branchiostegal rays. Counts of bilaterally symmetrical features were made on the left side of the body. Osteological characters were examined from specimens cleared and stained (cs) according to the procedure of Dingerkus & Uhler (1977). Vertebral counts include only free centra, with the compound caudal centra (pleural 1 + ural 1) counted as a single element. Institutional abbreviations are as in Leviton et al. (1985), with the addition of MZUEL (Museu de Zoologia da Universidade Estadual de Londrina), LBP (Laboratório de Biologia de Peixes da Universidade Estadual Paulista  campus de Botucatu), and LIRP (Laboratório de Ictiologia de Ribeirão Preto da Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto - Universidade de São Paulo). Other abbreviations are SL, standard length and HL, head length.

Color in alcohol. Ground color light brown alternating with slighty darker brown saddles on head and trunk. Darker area mottled with small light patches covering area on head from tip of snout to occipital region and extending ventrally onto interopercle and opercle. Large dark brown saddle located dorsally from nuchal region to posterior base of dorsal fin, center of saddle interrupted by small light brown patch over spinelet; saddle n-shaped in lateral view. Dark coloration on head and first dark saddle on body separated by lighter yoke-like marking across nuchal region. Second dark brown saddle extends from slightly posterior of dorsal fin to middle of adipose fin, center of saddle interrupted by large light brown oval patch over anterior third of adipose fin; dark saddle broadly v-shaped in lateral view. Irregular light brown vermiculations on sides along trunk. Dark brown band at base of caudal fin. Conspicuous dark brown band in middle of caudal fin. Dorsal fin with dark brown band across middle and another dark band along base. All fins and belly mottled with small dark brown spots.

Despite repeated collecting efforts in the rio Paraná basin in recent years, few specimens of M. garavelloi have been found, indicating that this might be a rare species (total = 65 individuals, mean = 3.8 per collection event).

Distribution. This species is known only from Brazil in the rio Paranapanema and rio Tietê basins (Fig. 4). In rio Paranapanema basin, M. garavelloi was collected in ribeirão Taquari, in Paraná State, and ribeirão Pau D'alho, tributary of rio Capivara, in São Paulo State. In the rio Tietê basin, it was collected in rio Pirapitingui, and Barreiro stream.

Results and Discussion. Microglanis garavelloi can be discriminated from M. parahybae and M. cottoides in the first canonical variate axis that explains 64.7% of the variance (Fig. 5 and Table 2). Microglanis garavelloi has a caudal-peduncle depth, pectoral-girdle width, interorbital width, head depth, and pelvic-fin length greater than that found in M. parahybae and M. cottoides (higher positive values of CVI, p = 0.0001). Microglanis cottoides and M. parahybae also have a pelvic-fin to anal-fin distance and eye diameter greater than M. garavelloi (higher negative values of CVI, p = 0.0001). In the analysis M. cottoides could be discriminated from the two other species by the second canonical axis, based on larger adipose-fin base length, eye diameter and pelvic-fin to anal-fin distance (higher positive value of CVII, p = 0,0013). It is noteworthy that there is some geographic correlation between morphometric variation and river system within species M. garavelloi and M. parahybae.

The results of our analysis corroborate the work of Malabarba & Mahler (1998) who considered the species M. cottoides and M. parahybae to be valid. Previously, Gomes (1946) applied the name M. cottoides to all populations of Microglanis of southern Brazil whereas Mees (1974) considered M. cottoides to be a junior synonym of M. parahybae. We note that the pectoral spine illustrated by Mees (1974, Fig. 40a) for M. parahybae is more similar to spines in specimens identified here as M. cottoides (Fig. 3). However, we agree with Mees (1974), that the form of the spine changes with ontogenetic development, exhibiting a gradual increase of the number of serrations with an increase in spine length. To minimize such changes, we compared specimens with pectoral spines similar in length. As shown in figure 3 the pectoral-spine serrations in M. garavelloi are more robust and less numerous than in M. parahybae and M. cottoides for similarly sized specimens.

The species of Microglanis in southern Brazil exhibit subtle differences in color pattern that can be useful for identification mainly because intra-populational polymorphism was not observed. The color pattern of M. garavelloi is very similar to that of M. parahybae (both present vermiculations, and a dark saddle in the adipose fin area that does not extend to the anal fin). These two species are best differentiated on the basis of caudal-peduncle depth (10.8-16.8% of SL in M. garavelloi vs. 9.8-11.4% in M. parahybae) and pectoral-girdle width (28.2-33.9% of SL in M. garavelloi vs. 25.6-29.7% in M. parahybae).

The identification of a new species endemic to the upper rio Paraná basin agrees with the hypothesis of Vari (1992), who considered this region to be an area of endemism. Other recently described species apparently endemic to the basin, such as Neoplecostomus paranensis Langeani, 1990 and Corumbataia cuestae Britski, 1997, reinforce this hypothesis. All of these species are characterized by their small size (less than 20 cm SL) and their occurrence in small streams. Nevertheless, it is possible that the apparently restricted distribution of M. garavelloi in the rio Tietê and rio Paranapanema basins may be the result of a lack of collecting efforts in small-river habitats of the upper rio Paraná basin. The occurrence of M. garavelloi at different sites in the upper rio Paraná suggests that the distribution of the genus in the Paraguay-Paraná basin may be broader than is presently known and tied to patchily distributed habitats. The utilization of more encompassing collecting techniques in a greater variety of habitats often reveals the presence of new species (Castro & Casatti, 1997). Castro & Menezes (1997) proposed that new species would be found with an increase of collections in upper rio Paraná basin.

Eigenmann, C. H. 1912. The freshwater fishes of British Guiana, including a study of the ecological grouping of species and the relation of the fauna of the plateau to that of the lowlands. Memoirs of the Carnegie Museum, 5(1): i-xxii, 1578, pls. 1-103. [ Links ]

Gomes, A. L. 1946. A review of Microglanis, a genus of South American catfishes, with notes on related genera. Occasional Papers of the Museum of Zoology, 494:1-19. [ Links ]